Struggling to keep vowel harmony consistent with case suffixes

I've been using a few different apps to drill Hungarian, but I keep tripping up when adding suffixes like -ban/-ben or -hoz/-hez/-höz to words that have mixed vowels. It feels like I'm hitting a wall where I have to pause and analyze every single word before I can speak. Does anyone have a mnemonic or a specific study method to make these vowel harmony shifts automatic instead of a mental calculation?